Apparatus for heating service water

ABSTRACT

An apparatus is described for heating service water with a solar collector, comprising a service water tank ( 7 ) with a partly cylindrical jacket ( 8 ) as an absorber and an enclosure ( 1 ) which covers the service water tank ( 7 ) and forms a translucent cylindrical jacket ( 3 ), the axis of which extends parallel to the axis of the jacket ( 8 ) of the service water tank ( 7 ). In order to provide advantageous heating conditions, it is proposed that the service water tank ( 7 ) is connected in a thermally conductive manner with an absorber plate ( 4 ) forming a bottom part of the enclosure ( 1 ) and that the absorber plate ( 4 ) and the jacket ( 8 ) of the service water tank ( 7 ) are covered with a wide-meshed, thermally insulating fabric ( 11 ).

FIELD OF THE INVENTION

The invention relates to an apparatus for heating service water with asolar collector, comprising a service water tank with a partlycylindrical jacket as an absorber and an enclosure which covers theservice water tank and forms a translucent cylindrical jacket, the axisof which extends parallel to the axis of the jacket of the service watertank.

DESCRIPTION OF THE PRIOR ART

If service water is to be heated with the help of solar power, solarcollectors are usually used which comprise a trough-like frame with abase plate acting as an absorber, on which parallel tubular flowchannels are provided for water as a heat carrier for example. Thetrough with the absorber plate and the flow channels which are connectedto a distribution and a collecting line is provided with a translucentcover, so that especially the thermal radiation is absorbed by theabsorber plate and the flow channels arranged thereon, and the absorbedheat is transferred to the heat carrier, with the help of which aservice water storage tank is charged via a heat exchanger. Thedisadvantageous aspect in such solar collectors is that a respectiveorientation is required with respect to solar radiation and that a hotwater storage tank is required for heating the service water, which hotwater storage tank is connected via a heat exchanger to the solarcollector.

In order to avoid these disadvantages it has already been proposed (DE20 2006 015 934 U1) to utilize the jacket of a cylindrical service watertank as an absorber and to provide the service water tank for thispurpose with an enclosure, the translucent jacket of which forms asemi-cylinder with an axis parallel to the axis of the tank. Thecylindrical shape of the service water tank leads to a substantialindependence of the apparatus from the angle of incidence of thesunlight in co-operation with the enclosure forming a jacket in form ofa semi-cylinder if the axis of the tank or the enclosure is alignedapproximately in a north-south direction, so that a substantially radialincidence of light into the enclosure is ensured. As a result of thetemperature-dependent density of the service water, the heated servicewater will accumulate in the upper region of the horizontally disposedservice water tank and can be withdrawn via an upper hot water pipe bysimultaneously supplying cold water in the base region. In order toreduce the thermal losses, the jacket of the enclosure is covered on theinside with a translucent knitted fabric in order to reduce the emissionof heat to the outside in the case of low outside temperatures.Moreover, efforts are made to better utilize the light entering theenclosure by a light-reflecting bottom part. However, despite thesemeasures efficiency remains limited.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of improving theefficiency in solar collectors in which the jacket of the service watertank is used as an absorber.

On the basis of an apparatus for heating service water of the kindmentioned above, the invention achieves this object in such a way thatthe service water tank is connected in a thermally conductive mannerwith an absorber plate forming the bottom part of the enclosure and thatthe absorber plate and the jacket of the service water tank are coveredwith a wide-meshed, thermally insulating fabric.

The provision of an additional absorber plate which forms the bottompart of the enclosure and which is connected with the service water tankin a thermally conductive manner provides a better utilization of thethermal radiation entering the enclosure because the absorber plateheated by this thermal radiation will pass on the absorbed heat to theservice water tank. Covering this absorber plate and the jacket of theservice water tank with a wide-meshed, thermally insulating fabricprevents direct contact of air flows formed as a result of convectionwithin the enclosure with the absorber plate and the service water tank,leading to a higher temperature of the absorber plate and a lowercooling of the service water tank and therefore to improved heatingconditions for the service water. The wide meshes of the fabric ensuredirect passage of thermal radiation to the absorber plate and to theservice water tank through the fabric, wherein especially favorableheating conditions are obtained when the fabric is permissible tothermal radiation itself, as is the case in a glass-fiber fabric.

In order to ensure an advantageous heat transmission between theabsorber plate and the service water tank, the absorber plate canaccommodate the service water tank in a cylindrical bulged portion whichsits close to the tank jacket, so that an enlarged heat transfer surfacearea is obtained. For fastening the service water tank, it can be weldedonto or soldered together with the absorber plate.

This construction is especially useful for service water tanks with acircular-cylindrical jacket. The invention is not limited to suchcircular-cylindrical service water tanks. Especially simpleconstructional conditions are obtained when the service water tank iscomposed of a jacket approximately forming a semi-cylinder and acylindrical wall connected to the inside of said jacket, the axis ofwhich extends perpendicularly to the jacket axis. Since as a result ofthis measure the service water tank can be produced from two sheet metalcuttings which are each cylindrically bent and then welded together witheach other, comparatively simple production conditions can bemaintained. The semi-cylindrical jacket of the service water tank whichcloses off the cylindrical wall of the service water tank to the outsideforms protruding edge sections at least in the connection area of thecylindrical wall, which edge sections represent an additional absorbersurface area which has an advantageous effect on the heat transmission,since the semi-cylindrical jacket of the service water tank can bearranged approximately co-axially with the jacket of the enclosure whichalso forms a semi-cylinder, so that the thermal radiation is alignedsubstantially radially with respect to the jacket of enclosure and thejacket of the service water tank, which therefore occurs substantiallyindependent of any change in the position of the sun during the day.

Advantageous connections of the service water tank to the absorber plateare obtained with a jacket of the service water tank in form of asemi-cylinder when the jacket of the service water tank is arrangedintegrally with the absorber plate.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter of the invention is shown in the drawing by way ofexample, wherein:

FIG. 1 shows a schematic cross-sectional view of an apparatus inaccordance with the invention for heating service water;

FIG. 2 shows this apparatus in a longitudinal sectional view along theline II-II of FIG. 1;

FIG. 3 shows an illustration corresponding to FIG. 1 of an embodiment ofan apparatus in accordance with the invention for heating service water,and

FIG. 4 shows the apparatus according to FIG. 3 in a sectional view alongthe line IV-IV of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the embodiment according to FIGS. 1 and 2, theapparatus for heating service water comprises a solar collector with anenclosure 1 which is composed of two semi-circular face walls 2 and ajacket 3 which is made of a translucent material and arched according toa half a circular cylinder. The bottom part of this enclosure 1 isformed by a thermally conductive absorber plate 4, which is preferablymade of a metallic material such as copper or aluminum, and is providedwith a thermal insulation 5 on the side facing away from the jacket 3.In the region of the cylinder axis of the enclosure 1, the absorberplate 4 forms a cylindrical bulging portion 6 which accommodates ahorizontally disposed, cylindrical tank 7, the axis of which extendsparallel to the axis of the enclosure 1. The arrangement is made in sucha way that the jacket 8 of the service water tank 7 rests in a planarmanner on the cylindrical bulging portion 6 of the absorber plate 4,which thereby ensures advantageous heat transmission from the absorberplate 4 to the tank jacket 8.

The service water tank 7 is connected at the bottom with a cold waterpipe 9 and at the top with a hot water pipe 10, so that wateraccumulating in the upper region of the service water tank 7 can bedischarged via the hot water line 10 under simultaneous supply of coldwater into the bottom region of the service water tank 7, which as aresult of the illustrated arrangement forms a service water tank withinthe enclosure 1 with a conventional temperature stratification of theservice water. In the event that several apparatuses of this kind areswitched in series, the individual service water tanks 7 are providedwith cold water pipes 9 and hot water pipes 10 on the mutually oppositeface sides, as is shown in FIG. 2. This connection in series allowstemperature compensation over the individual service water tanks 7,which is important especially when erecting the individual apparatusesat different height levels. When the apparatuses are used individually,the pipes 9 and 10 are sealed or omitted on one side.

Since the apparatus is advantageously erected in such a way that theaxis of the enclosure 1 or the service water tank 7 extendsapproximately in the north-south direction, a substantially radialincidence of light is obtained during daily solar radiation, so thatadvantageous conditions concerning thermal radiation are provided, whichapplies not only to the absorber plate 4 but also to the service watertank 7. In order to improve these heating conditions, the absorber plate4 and the jacket 8 of service water tank 7 are covered with awide-meshed, thermally insulating fabric 11, as is indicated with thedot-dash line in FIG. 1. The meshes of this fabric 11 prevent an airflow directly along the service water tank 7 and the absorber plate 4 asa result of air cushions caught within the meshes of the fabric. Thismeans that the air flows caused by convection within the enclosure 1will not have a disadvantageous effect on the heat transmission in theregion of the absorber plate 4 or the service water tank 7. The coarsemeshes of the fabric 11 facilitate the passage of thermal radiationthrough the fabric 11, with advantageous constructional conditions beingobtained especially in the case of glass-fiber fabrics because in thiscase the fabric 11 is permeable itself for the thermal radiation.Efficiency can additionally be improved by applying such a wide-meshed,thermally insulating fabric 11.

The relevant difference between the embodiments according to FIGS. 1 and2 on the one hand and FIGS. 3 and 4 on the other hand consists of theconstruction of the surface water tank 7. Whereas the jacket 8 of theservice water tank 7 according to FIGS. 1 and 2 forms an enclosedcircular cylinder, the jacket 8 of the service water tank 7 according toFIGS. 3 and 4 is arranged in form of a semi-cylinder which extendssubstantially coaxially to the jacket 3 of the enclosure 1. Thissemi-cylindrical jacket 8 of the service water tank 7 outwardly seals awall 12 which is open towards said jacket 8, with the arrangement beingmade in such a way that the semi-cylindrical jacket 8 of the servicewater tank 7 protrudes on both sides in the axial direction beyond thecylindrical wall 12, as is shown in FIG. 4. The axis of the cylindricalwall 12 extends perpendicularly to the axis of the semi-cylinder of thejacket 8.

As a result of this arrangement, the light radiation which enterssubstantially radially through the jacket 3 of the enclosure 1 alsoimpinges substantially radially on the jacket 8 of the service watertank 7, thereby providing advantageous heating conditions for the jacket8 of the service water tank 7, which forms a comparatively largeabsorber surface. Since the absorber plate 4 according to FIG. 3 isintegrally arranged with the jacket 8 of the service water tank 7, anadvantageous heat transfer from the absorber plate 4 to the jacket 8 ofthe service water tank 7 is ensured. The absorber plate 4 and the jacket8 of the service water tank 7 are covered with a wide-meshed, thermallyinsulating fabric 11, preferably a glass-fiber fabric, as in theembodiment according to FIGS. 1 and 2, in order to prevent as far aspossible any thermal losses by heat dissipation to the intermediatespace between the service water tank 7 and the enclosure 1.

1. An apparatus for heating service water with a solar collector,comprising a service water tank (7) with a cylindrical jacket (8) as anabsorber and an enclosure (1) which covers the service water tank (7)and forms a translucent, partly cylindrical jacket (3), the axis ofwhich extends parallel to the axis of the jacket (8) of the servicewater tank (7), wherein the service water tank (7) is connected in athermally conductive manner with an absorber plate (4) forming a bottompart of the enclosure (1), and wherein the absorber plate (4) and thejacket (8) of the service water tank (7) are covered with a wide-meshed,thermally insulating fabric (11).
 2. An apparatus according to claim 1,wherein the fabric (11) consists of a glass-fiber fabric.
 3. Anapparatus according to claim 1, wherein the absorber plate (4)accommodates the service water tank (7) in a cylindrical bulging portion(6) sitting close to the tank jacket (8).
 4. An apparatus according toclaim 1, wherein the service water tank (6) is composed of a jacket (8)which approximately forms a semi-cylinder and a cylindrical wall (12)which is connected to the inside of the jacket (8) and whose axisextends perpendicularly to the jacket axis.
 5. An apparatus according toclaim 4, wherein the jacket (8) of the service water tank (7) isintegrally arranged with the absorber plate (4).